Conventional irrigation systems are intended to periodically replenish accumulated soil water deficits which are associated inter alia with the water retention capacity of the soil, the type of the plants and environmental conditions.
Various proposals have been made and, in some cases implemented, to provide an irrigation system designed to be responsive to the water status of the soil. Thus, for example, it is known to monitor the relative humidity in the soil and to arrange for the irrigation system to be responsive to this relative humidity.
It is known that changes in the water status of a plant are reflected in dimensional changes in one or other of the plant's component elements such as leaves, stalks or stems, and fruits, etc. It has been proposed to monitor such changes and to arrange for periodic irrigation in response to such changes. Of these plant organs, it has been particularly proposed to utilize changes in a leaf's thickness for controlling an irrigation system seeing that it is believed that the instantaneous water status of a leaf of a plant as represented by its thickness provides an accurate indication of the instantaneous water status of the plant.
It is therefore clear that in order to provide for an efficiently operating irrigation system responsive to leaf thickness sensing, it is of prime importance to have available a reliable and efficient leaf thickness sensing device.
It is therefore an object of the present invention to provide a leaf thickness sensing device primarily for use in irrigation systems.